The present invention relates to a multi-functional control valve system for a liquid petroleum gas (LPG) tank.
With the increased modern day emphasis on LPG such as propane for fuels, there has been a need for increased safety and convenience in the handling of LPG both commercially and domestically. Thus, for example, new cars are being manufactured and old cars are being adapted, to run on LPG. LPG systems require the fuel to remain in liquid state until the fuel is actually about to be converted to energy through combustion. This requires the fuel tank and delivery lines to be maintained under relatively high pressure. This means that, cars, conventional gasoline storage and delivery systems, including holding tanks, delivery lines, fuel gauges, filling ports and the like, cannot be used for LPG. Also, when LPG tanks are filled, again because of the pressure conditions under which the fuel must be maintained, problems of overfilling of the fuel tank and spillage of fuel leading to hazardous conditions during the filling process, become significant. Again, because of the pressures involved, leakage around inlet and outlet valves of conventional LPG fuel storage tanks creates a serious problem.
Conventional LPG storage and delivery systems for example used on cars, trucks, forklifts and the like until now have required multiple ports, for example for filling, for fuel delivery to the combustion area, for bleeding to warn of overfilling, and for pressure relief. At each of these ports, control problems such as leakage of gas, may potentially arise.
Prior references of general background interest with respect to the present invention include Canadian Patent No. 912,431 issued Oct. 17, 1972 of Tappin, which describes and illustrates safety cut-off equipment for burners designed for bottled propane and similar LPG fuels; Canadian Patent No. 982,445 of Nelson issued Jan. 27, 1976 which describes and illustrates a shut-off valve assembly, albeit for gasoline supply lines at gasoline filing stations, and Canadian Patent No. 1,087,067 of Hughes issued Oct. 7, 1980 relating to a relay pilot regulator having combined loading and unloading valves which share a common operating linkage.
It is an object of the present invention to provide a control valve system for an LPG tank which is unique in construction and which overcomes many of these problems previously encountered with control valve systems for LPG tanks.